Art of vulcanizing rubber



PATENT. OFFICE.

mirror om FORTH, TALLHADGI TOWNSHIP, AND WILLIAH CHRIS- mm, OI AKRON,OHIO, ASSIGROBS TO THE RUBBER 00., Oil AKRON, OHIO, A OOBPORATION OIOHIO.

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. Our invention is directed tothe art of accelerating the vulcanizationof 'rubber and is particularly directed to the use of certain types ofcompounds produced-by the interaction of unsaturated aldehydes uponamines as accelerators of vulcanization as is hereinafter set-forth.

More. particularly our invention is directed to the use as acceleratorsof the vulcanization process of com unds prepared by the interaction ofan a ditional quantity of an unsaturated aldehyde upon the type ofcompounds prepared as described in our Patent No. 1,67 0,312, grantedMay 22, 1928.

Accordin to the disclosure of this patent we have ound that valuableaccelerators oi the vulcanization of rubber may be obtained by theinteraction of equi-molecular quantities of any primary aromatic aminewith an unsaturated straight chain aldehyde containing preferably'notmore than seven and not less than three carbon atoms. These simplereaction products so produced may be reacted with an'additional quantityof the 2 same'or a difierent aldehyde andpreferably with an unsaturatedaldehyde to produce other compounds of complex chemical compositionwhich we'have found to be particularly valuable when used asvulcanization 3o accelerators in the manner as hereinafter set forth.Our compounds may, then, be described as, the aldehyde derivatives ofSchifi"s bases wherein either or both of the aldehydes used areunsaturated.

TlllS new type of com unds, that is, the aldehyde reaction products ofthe condensation products of unsaturated straight chain aldeh des withprimary aromatic amines may be most readily prepared by heating togetherover the water or steam bath a mixture of a primary aromatic amine witha greater quantity of the aldehyde than is required to produce a simplecondensation product. Thus, for example, aniline and croton-aldehyde maybe mixed in the proportion of 93 70 parts of t e aldehyde and themixture heated'over a vboiling water bath and maintained atthatJteinerature for a period of time (about three ours) until it is certain thatthe reaction is completed, whereupon thewater of condensation formed inthe reaction is more or less completely removed by evaporation andtheproduct is further cally or completely freed of water.

parts of aniline and more than.

Application, am Kay 19, m4. leriala... 114,460.

heated at a temperature .no higher 110 centigrade until the material isractie material may-also be produced in a two stage rocess, 1f desired,as-is shown by the folowlng example.-

An amine, such as aniline and an unsaturatedaldeh'yde such ascroton-aldehyde may be heated together'in equi-molecular pro rtions.(that is, 93 parts of the aniline an parts of the proton-aldehyde). Themixture is heated over the boili water bath as before for a period ofsome ours, whereby a simple condensation product is formed. Before orsubsequent to the removal of water of condensation, a further 'uantityof'the same or a difi'erent aldehyde 1s added tothe.

mixture and the heating continued under the same conditions as before.Further condensation takes place and there. is formed the aldehydereaction product of an unsaturated aldehyde and an amine. The waterpresent in the mixture is now more or less completel y removed bycareful heat treatment of the product at a temperature no higher than110 centigrade, whereupon the comparative-f 1y solid product obtained isready-for incorporation into a rubber mix.

It is evident'to those skilled in theart that other methods may be usedin preparing my preferred class of compounds without departing from thespirit of the invention. Other amines and aldehydes than those cited inthe examples given may also be used. Thus, for example, we may combineany primar aromatic amine, such as aniline a toluidine, a. xylidene,naphthylamine, amino cymene and'the like with equal molecularproportions of any unsaturated aldehyde such as acrolein,croton-aldehyde, guaiacol, methyl-ethyl-acrolein, propargylic aldehydeand the like and then further react the product obtained with anadditional quantity of the same or a different unsaturated aldehyde orwith an excess of a saturated aldehyde such as formaldehyde,acctaldehyde, thepolymeric aldehydes such as paraldehyde, or'

other aldehydes of the aliphatic series of organic compounds.Furthermore -itis possible to prepare a simple condensation prodrated asregards the hydrocarbontnucleus to prepare the secondary compound. Thus,We may react equi-molecular quantities of o-toluidine or other primaryaromatic amine with croton-aldehyde, acrolein' or other unsaturatedaldehyde and then react the product so formed with an excess offormaldehyde, acetaldehyde or other Straight chain aliphatic aldehydes.As another instance of the possible compounds we may use in our process,we mention the product obtained by the action of formaldehyde oracetaldehyde on the reaction product of acrolein and an aromatic primaryamine.

Whatever the method used in preparing the compounds of the typesetforth'wherein an aromatic primary amine has been reacted with an excessof a straight chain unsaturated aldehyde the method of using thesetures.

compounds as accelerators of "he vulcanization of rubber is the same.Thus, for example, 100 parts of smoked sheet rubber, 3.5 parts of.sulfur, 5 parts of zinc oxide and 1 part of accelerator are milledtogether in the well known manner on the differential mixing mills. Thismixis then heat treated in the vulcanization press under a steampressure of 4:0 pounds per square inch for about twenty minutes and agood vulcanized product results. The composition prepared as justdescribed comprises a basis for a friction and coat stock. Thevulcanized prod uct possesses good low temperature characteristics andgives a product possessing a good technical cure. The lowest undercureof technical value for the stock described above is obtained byvulcanizingfor about ten minutes at 20 pounds steam pressure per squareinch. For a friction stock for use in a large pneumatic tire there isneeded a composition that cures rapidly at low tempera- Since thecomposition described gives a product when vulcanized at 20 pounds steampressure per square inch which possesses the required characteristicsand pro erties, this stock prepared as shown in t e above example and bythe use of our 'preferred class of accelerators comprises an excellentfriction stock.

Another example illustrative of the use of our new class of acceleratorsis in the manufacture of a rubber stock which may be used ture of 100 inthe carcass of a rubber tire, for example, in a cover stock which isplaced on top of the breaker strip of a pneumatic tire. I For thepreparation of a mixture intended for this purpose, we may mill-togethera mixarts of smoked sheet rubber, 4 parts'of sul ur, 40 parts of zincoxide and 1 part of our new type of accelerator, for example, theproduct produced by the action of croton-aldehyde onthe condensationprodnot of croton-aldehyde and aniline. This mixture is then vulcanizedfor about 20 minutes in a vulcanizing press under 40 pounds steampressure per 3 square inch in which we inten whereupon the resultingvulcanized product is found to possess a tensile strength in excess of3000 pounds per square inch. The ultimate elongation is about 800%,while the load necessary to produce ':300%: elongation is about 300pounds per squareinch,

Our new class of accelerators may be used for the manufacture of othertypes of compounds, such as a hard rubber. Illustrative of anotherrubber compound prepared by the use of our new accelerators, we maymention the following which represents a typical tread stock, We milltogether in the well known manner 53 arts of smoked sheet rubber, 19parts of car on black,-20 parts of zinc oxide, 2 parts of sulfur,'1 partof any of our new class of accelerators, 1 part of hardwood pitch.(Fluxol), 1 part of a blended oil (C cline) and 3 parts of mineralrubber. T 1is'mixture,. after vulcaniza tion for about one hour at 40pounds steam pressure per square inch, yields a product possessing atensile strength of approximately 4000 pounds 'per square inch, havingan ultimate elongation of approximately 700% while the load necessary tocause an elongation of 300%; is approximately 1000 pounds per s uareinch.

Alt oug-h we have set forth the preferred methods whereb ouraccelerators of vulcanization may e prepared and have ,de-

scribed several examples illustrative of the ods of using our newcompounds as accel-" ,erators in the manufacture of vulcanized rubberare apparent to those skilled in the art and it is our intention toinclude all such methods, as well asYthose set forth in the foregoingexamples, as falling within the scope of our invention and as covered bythe claims appended hereto. ;Furthermore, it is to beunderstood-that-our invention is not limited by the, accuracy of anytheories advanced in explanation of vthe .various phases of ourinvention but that the invention is limited solel by the followingclaims (f to. define and claim our. y as is permissible in viewinvention as broadl of the prior art.

What we claim is:

1. The process which consists in incorporating a small percentage of thealdehyde.

reaction product of the condensation product of an aromatic primaryamine and 1111 um saturated aliphatic aldehyde containing less than eiht'carbon atoms into a rubber mixture and heating with a vulcanizingagent.

2. The process which consists in incorporating a small percentage of thealdehyde reaction product of the condensation product of an aromaticprimary amine and an unsaturated aliphatic aldehyde containing more thantwo and less than eight carbon atoms into a rubber mixture and heatingwith a vulcanizing agent.

3. The process which consists in corporat-ing a small percentage of thealdehyde reaction product of the product obtained by reacting togetheraniline and croton-aldehyde into a rubber mix and heating with avulcanizing agent.

4. The process which-consists in incorporating a small ercentage of thereaction product obtained by reacting croton-aldehyde on thecondensation product of aniline and croton-aldehyde into a rubbermixture and heating with a vulcanizing agent.

5. The process which consists in incorporating a small percentage of theproduct obtained by reacting aniline with more than an equal molecularproportion of crotonaldehyde into-a rubber mixture and heating with avulcanizing agent.

6. The process which consists in incorporating a small percentage of theproduct ob- .tained. by reacting aniline with an excess ofcroton-aldehyde into a rubber mixture and heating with a vulcanizingagent.

7. The process .which consists in incorporating into a rubber mixture asmall percentage of the product obtained by reacting with an aldehyde, aSchifls base prepared by reacting an aromatic primary amine with anunsaturated aldehyde containing from three to seven carbon atoms andheating the mixture so formed with a vulcanizing agent.

8. The process which consists in incorporating a small percentage of thecroton-aldehyde reaction product of a Schifls base prepared by reactinga primary aromatic amine with an unsaturated aliphatic aldehyde into arubber mixture and heating with a vulcanizing agent.

9. A rubber combined with the aldehyde derivative of the reactionproduct of a primary aromatic 'amine and an unsaturated aliphaticaldehyde containing from three to'seven carbon atoms and vulcanized.-

10. A rubber product derived from rubber, combined with the aldehydederivative of the condensation product of aniline and croton-aldehyde,and vulcanized.

11. The process of manufacturing an accelerator for use in vulcanizingrubber comproduct derived from rubber,

13. The process of manufacturing an accelerator for use in vulcanizingrubber comprising reacting with croton-aldehyde the condensation productof croton-aldehdye and aniline.

14. A rubber product derived from rubber, combined with the aldehydereaction product of the condensation product of an aromatic primaryamine and an unsaturated aliphatic aldehyde containing more than two andless than eight carbon atoms and vulcanized.

CLAYTON OLlN NORTH.

CHESTER WILLIAM CHRISTENSEN.

